Pipettes used for liquid dosage in laboratories comprise a piston movable in a cylinder for aspiration of liquid into a pipette tip connected with the cylinder. Such pipettes comprise an elongated handle held by palm grip. The volume is usually adjustable. Typically, there is also a mechanism for removing a used tip from the pipette. There are also multichannel pipettes comprising eight channels in a row. In manual pipettes, all the operations are carried out by hand force. The piston in almost all manual pipettes is moved by pushing with thumb a spring-loaded rod placed at the upper end of the pipette. Volume is usually set by rotating the knob. The tip is removed by pushing a spring-loaded push button at the side of the handle. There are also electronic pipettes in which the piston is actuated by means of an electric motor. The tip removal mechanism is still often manual, but there are also electronic pipettes in which also the tip removal mechanism is electrically driven. There may also be manual pipettes operated by hand force but comprising an electronic display.
Manual pipettes are described in European Patent Application No. EP 112 887 and electronic pipettes are described in European Patent Application No. EP 1 725 333.
An example of an electronic pipette is Finnpipette® Novus Electronic Pipette (Thermo Fisher Scientific Oy, Finland). This pipette contains also a counter which counts the total number of pipettings after the latest calibration. The user may go and check that number and consider whether recalibration is appropriate. After the recalibration, the counter is automatically reset.
Ergonomics is an important factor in pipetting. A typical user in a laboratory may have to make hundreds of repetitive pipetting series during a working day. The forces needed to move the piston and tip remover may be quite big especially in multichannel pipettes. The distance that the piston rod must be moved may be quite long in relation to the anatomy of a user's hand. In electric pipettes, the piston is not moved by hand force, but instead by operating a switch. The weight of an electric pipette is, however, usually bigger. Pipetting needs also often very accurate movements when liquid is taken from and dispensed into small vessels. This causes extra workload.